A touch panel has heretofore been used for ATMs in banks, game machines in video arcades, and ticket vending machines for trains, buses, and the like. When the touch panel is produced by mounting a touch sensor in a display device, it is possible, by virtue of the construction of the touch panel, to intuitively operate the machine through visual perception of information displayed on the display device. Therefore, the device mounted with the touch panel has an advantage in that the device can be easily operated.
In addition, the touch panel enables mounting of an input device in a display device, and hence obviates the need to separately provide an input device, thus enabling downsizing and light-weighting of the entire device. Therefore, in recent years, the touch panel has been suitably used for mobile phones, smartphones, portable game consoles, tablet PCs, and notebook PCs, downsizing and light-weighting of which have been demanded.
The touch panel adopts any of various systems such as a resistive system, a surface acoustic wave system, an infrared system, an electromagnetic induction system, and a capacitive system in accordance with its intended use. For the purpose of enabling simultaneous detection of a plurality of positions, in recent years, the touch panel based on the capacitive system has been adopted for smartphones, tablet PCs, and the like.
In the touch panel based on the capacitive system, two perpendicular transparent conductive layers are provided on both front and back surfaces of a transparent dielectric, and when an operator brings a conductor such as a finger into contact with the touch panel, a change in capacitance of an electrode at a contact position can be detected on the basis of two lines of electrodes, i.e., row and column electrodes. Thus, the contact position can be precisely determined. In order to form the transparent conductive layers, a transparent substrate is required to have heat resistance enough to endure high temperature during formation of the transparent conductive layers. In general, a glass substrate is desirably used as the transparent substrate. In addition, in order to achieve downsizing and light-weighting of the touch panel device, thinning of the glass substrate to be used for the touch panel is desired. Patent Literature 1 below describes that when film-forming treatment is performed on a glass film having a thickness of 200 μm or less, the glass film is supported with a supporting glass.
Meanwhile, in addition to the functional aspects such as downsizing and light-weighting of the device, in recent years, there has been a demand for the device mounted with the touch panel to have novel property in design such as harmony with its installation space or cool appearance. Although many of the related-art display devices assume flat surface shapes, in order to attain a satisfactory degree of freedom in design, a display device assuming a curved shape has been demanded, and a touch panel curved so as to fit the display device has also been demanded as described in Patent Literature 2 below. In Patent Literature 2 below, the curved touch panel is mounted onto a surface of a liquid crystal display device having a curved shape and a protective sheet is provided on its surface.